No sound in earphones

Hi guys, I have recently bought new earphones, they worked good. Then I borrowed it to my friend cause she lost hers, and when she returned them, they weren't working properly. I had to move input plug, then they worked good but sometimes I must have done it more times because i heard just background music with buzzing but no speaking. But today I was trying it again first they only worked with right earbud. Now they aren't working at all. I don't hear any sound, only at right earbud if I move input plug but when I release it I don't hear anything. I can't look into input plug. Can it be repaired somehow? I know it's maybe stupid question but I just wanna know how pissed should I be at my friend.